Servers communicate trough HTTP Response Codes, these are status codes used to tell search engines and browsers, whether a requested resource exists, has been moved permanently or temporarily.
The below is a table of common HTTP Response Codes.
|200 OK||The server returned the resource successfully.|
|201 Created||The request has been fulfilled and resulted in a new resource being created.|
|202 Accepted||The request has been accepted for processing, but the processing has not been completed.|
|203 Non-Authoritative Information||The returned metainformation in the entity-header is not the definitive set as available from the origin server, but is gathered from a local or a third-party copy.|
|204 No Content||The server has fulfilled the request but does not need to return an entity-body, and might want to return updated metainformation.|
|205 Reset Content||The server has fulfilled the request and the user agent SHOULD reset the document view which caused the request to be sent.|
|206 Partial Content||The server has fulfilled the partial GET request for the resource. The request must have included a Range header field.|
|304 Not Modified||The resource has not been modified, and no response body is sent.|
Here are some of the common redirection codes. Most of these response codes should be sent a long with a location for the new resource, which should be provided in the location header.
|301 Moved Permanently||The resource has Permanently moved, and future requests should be made for the given URL.|
|302 Found||The resource is temporarily located at a different location, and since this location may change from time to time, the client should continue to use the original URL for future requests.|
|303 See Other||The response for the request can be found at a different URL.|
These are some of the common error codes send by servers.
|400 Bad Request||The syntax of the request was bad, and the client should not repeat the request without modifications.|
|401 Unauthorized||The request requires a user to be logged in, the response must include a WWW-Authenticate header field.|
|403 Forbidden||The server understood the request, but is refusing to fulfill it. I.e. The user entered a wrong username or password.|
|404 Not Found||The requested resource could not be found. I.e. Nothing can be found here, i have looked absolutely everywhere technically possible, and nothing can be found.|